Carbonyloxy-substituted azulenesquaric acid dyes, intermediates therefor and optical recording medium

ABSTRACT

Carbonyloxy-substituted azulenesquaric acid dyes of the formula ##STR1## where L is C 1  -C 12  -alkylene which may be substituted by phenyl, 
     R 1  is C 1  -C 12  -alkyl, monounsaturated or polyunsaturated C 3  -C 12  -alkenyl, which may be phenyl-substituted, C 3  -C 7  -cycloalkyl, C 3  -C 7  -cycloalkenyl, substituted or unsubstituted phenyl, pyrrolyl, furanyl, thienyl or pyridyl and 
     R 2 , R 3 , R 4  and R 5  are each independently of the others hydrogen or substituted or unsubstituted C 1  -C 12  -alkyl, 
     with the proviso that when R 3  is hydrogen the positions of the substituents CH 2  --L--O--CO--R 1  and R 4  on either or both azulene rings may also be interchanged with each other within an azulene ring, are useful in an optical recording medium.

The present invention relates to novel carbonyloxy-substitutedazulenesquaric acid dyes of the formula ##STR2## where L is C₁ -C₁₂-alkylene which may be substituted by phenyl,

R¹ is C₁ -C₁₂ -alkyl, monounsaturated or polyunsaturated C₂ -C₁₂-alkenyl, which may be phenyl-substituted, C₃ -C₇ -cycloalkyl, C₃ -C₇-cycloalkenyl, substituted or unsubstituted phenyl, pyrrolyl, furanyl,thienyl or pyridyl and

R², R³, R⁴ and R⁵ are identical or different and each is independentlyof the others hydrogen or C₁ -C₁₃ -alkyl which may be substituted byhalogen, C₁ -C₁₂ -alkoxy, phenyl, substituted phenyl, C₁ -C₁₂-alkoxycarbonyl or by cyano,

with the proviso that when R⁵ is hydrogen the positions of thesubstituents CH₂ --L--O--CO--R¹ and R⁴ on either or both azulene ringsmay also be interchanged with each other within an azulene ring; tointermediates therefor; and to an optical recording medium whichcontains the novel dyes.

The cost-efficient manufacture of optical data recording media requiresdyes having particular properties. These dyes should

be strongly absorbing within the range from 700 to 900 nm to providelayers that may be writable with semiconductor lasers,

in layer form be highly reflective in the near infrared (700-900 nm) tomake possible a simple layer construction (without reflector layer),

be highly soluble, for example in order that the thin storage layer maybe applied to a base material by spincoating, and

be highly stable in thin layers.

The prior art storage materials frequently are defective on at least onecount.

It is an object of the present invention to provide novel dyes which arefree or substantially free of the abovementioned defects.

We have found that this object is achieved by thecarbonyloxy-substituted azulenesquaric acid dyes of the formula Idefined at the beginning.

Any alkylene and alkyl appearing in the abovementioned formula I may beeither straight-chain or branched.

In any substituted phenyl appearing in the formula I, suitablesubstituents are for example C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy and halogen(preferably fluorine, chlorine or bromine).

L is for example methylene, ethylene, 1,2- or 1,3-propylene, 1,2-, 1,3-,2,3- or 1,4-butylene, pentamethylene, hexamethylene, heptamethylene,octamethylene, nonamethylene, decamethylene, undecamethylene,dodecamethylene, phenylethylene or 1-phenyl-1,3-propylene.

R¹, R², R³, R⁴ and R⁵ in the formula I are each for example methyl,ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl,heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl or dodecyl.

R¹ may also be for example ethenyl, propenyl, butenyl, butadienyl,pentenyl, pentadienyl, hexenyl, hexadienyl, hexatrienyl, heptenyl,heptadienyl, heptatrienyl, ocetenyl, octadienyl, octatrienyl,octatetraenyl, nonenyl, nonadienyl, nonatrienyl, nonatetraenyl, decenyl,decadienyl, decatrienyl, decatetraenyl, decapentaenyl, undecenyl,undecadienyl, undecatrienyl, undecatetraenyl, undecapentaenyl,dodecenyl, dodecadienyl, dodecatrienyl, dodecatetraenyl,dodecapentaenyl, dodecahexaenyl, styryl, cyclopentyl, cyclopentenyl,cyclopentadienyl, cyclohexyl, cyclohexenyl, cyclohexadienyl,cycloheptyl, cyclopentenyl, chcloheptadienyl or cycloheptatrienyl.

R², R³, R⁴ and R⁵ may each also be for example fluoromethyl,chloromethyl, difluoromethyl, trifluoromethyl, trichloromethyl,2-fluoroethyl, 2-chloroethyl, 2-bromoethyl, 1,1,1-trifluoroethyl,heptafluoropropyl, 4-chlorobutyl, 5-fluoropentyl, 6-chlorohexyl,cyanomethyl, 2-cyanoethyl, 3-cyanopropyl, 2-cyanobutyl, 4-cyanobutyl,5-cyanopentyl, 6-cyanohexyl, 2-methoxyethyl, 2-ethoxyethyl,2-propoxyethyl, 2-isopropoxyethyl, 2-butoxyethyl, 2-methoxypropyl,2-ethoxypropyl, 3-ethoxypropyl, 4-ethoxybutyl, 4-isopropoxybutyl,5-ethoxypentyl, 6-methoxyhexyl, benzyl, 1-phenylethyl, 2-phenylethyl,4-chlorobenzyl, 4-methoxybenzyl, 2-(4-methylphenyl)ethyl,methoxycarbonylmethyl, ethoxycarbonylmethyl, 2-methoxycarbonylethyl,2-ethoxycarbonylethyl, 3-methoxycarbonylpropyl, 3-ethoxycarbonylpropyl,4-methoxycarbonylbutyl, 4-ethoxycarbonylbutyl, 5-methoxycarbonylpentyl,5-ethoxycarbonylpentyl, 6-methoxycarbonylhexyl or 6-ethoxycarbonylhexyl.

Preference is given to azulenesquaric acid dyes of the formula I whereR², R³, R⁴ and R⁵ are each C₁ -C₆ -alkyl or hydrogen.

Preference is further given to azulenesquaric acid dyes of the formula Iwhere R¹ is C₁ -C₁₂ -alkyl or C₂ -C₁₂ -alkenyl.

Particular preference is given to azulenesquaric acid dyes of theformula I in which R³ and R⁴ are each methyl, R³ and R⁵ are eachhydrogen, and L and R¹ are each as defined above. These dyes conform tothe formula Ia ##STR3##

Very particular preference is given to azulenesquaric acid dyes of theformula I where R² and R⁴ are each hydrogen, R³ is isopropyl, R⁵ ismethyl, and L and R¹ are each as defined above. These dyes conform tothe formula Ib ##STR4##

Preference is further given to azulenesquaric acid dyes of the formula Iwhere R¹ is C₁ -C₁₂ -alkyl or C₂ -C₁₂ -alkenyl.

The dyes of the formula I are obtainable for example from azulenederivatives of the formula I, where L, R¹, R², R³, R⁴ and R⁵ are each asdefined above by reaction with squaric acid of the formula III accordingto the following equation: ##STR5##

In those azulene derivatives of the formula II where R⁵ is hydrogen, thebond to the squaric acid can form at different positions on thefive-membered ring, which may produce isomeric products in which thering positions of substituents CH₁ --L--O--CO--R¹ and R⁴ areinterchanged with each other, as mentioned above. This is because it isthen necessary to distinguish those compounds where the bond to thesquaric acid forms on that side where the substituent CH₃ --L--O--CO--R¹is attached from those in which the bond to the squaric acid forms atthat side where the substituent R⁵ is attached. These isomeric compoundscan be separated by chromatography. For use in storage layers, however,it is customary to use the isomeric mixtures.

The method of preparation is known per se and is described for examplein Angew. Chem. 78 (1966), 937, and in EP-A-310,080.

The present invention further provides novel carbonyloxy-substitutedazulenes of the formula II ##STR6## where L is C₁ -C₁₂ -alkylene whichmay be substituted by phenyl,

R¹ is C₁ -C₁₂ -alkyl, monounsaturated or polyunsaturated C₂ -C₁₂-alkenyl, which may be phenyl-substituted, C₂ -C₂ -cycloalkyl, C₃ -C₇-cycloalkenyl, substituted or unsubstituted phenyl, pyrrolyl, furanyl,thienyl or pyridyl and

R², R³, R⁴ and R⁵ are identical or different and each is independentlyof the others hydrogen or C₁ -C₁₂ -alkyl which may be substituted byhalogen, C₁ -C₁₂ -alkoxy, phenyl, substituted phenyl, C₁ -C₁₂-alkoxycarbonyl or by cyano.

Concerning examples of L, R¹, R², R³, R⁴ and R⁵, reference is made tothe previous lists.

The carbonyloxy-substituted azulene derivatives of the formula II areobtained by starting from the corresponding hydroalkylazulenederivatives of the formula IV ##STR7## where L, R², R³, R⁴ and R⁵ areeach as defined above. The preparation of these products is describedfor example in EP-A-310,080.

For instance, those azulene derivatives of the formula IVa or IVb##STR8## where L is in each case as defined above, are particularlyhighly suitable for conversion.

The conversion of the hydroxyalkylene derivatives IV can be effected forexample with organic carboxylic acids or carbonyl halides of the formulaV

    R.sup.1 --CO--X                                            (V)

where R¹ is as defined above and X is hydroxyl or halogen, in aconventional manner. To this end, the hydroxyalkylazulene IV can bereacted for example with a carbonyl chloride V (X=chlorine) in an inertorganic solvent (e.g. methylene chloride, 1,1,2-trichloroethane,toluene, naphtha or tetrahydrofuran) at from 0° to 80° C. in thepresence or absence of a base (for example a tertiary amine orpyridine). The hydroxyalkylazulene IV can also be converted with acarboxylic acid V (X=hydroxyl) in the presence of a condensing agent,e.g. dicyclohexylcarbodiimide, and in the presence or absence of acatalyst (e.g. dimethylaminopyridine) under the aforementionedconditions.

It is a further object of the present invention to provide a noveloptical recording medium containing azulenesquaric acid derivatives asstorage materials which is simple to manufacture, is easy to write toand subsequently also to read back from, for which the signal-to-noiseratio should be very high, and which exhibits high storage layerstability.

We have found that this further object is achieved by an opticalrecording medium comprising a base material and a radiation-sensitivethin coating film which contains a dye with or without a binder, whereinthe dye has the formula I ##STR9## where L is C₁ -C₁₂ -alkylene whichmay be substituted by phenyl,

R¹ is C₁ -C₁₂ -alkyl, monounsaturated or polyunsaturated C₂ -C₁₂-alkenyl, which may be phenyl-substituted, C₃ -C₇ -cycloalkyl, C₃ -C₇-cycloalkenyl, substituted or unsubstituted phenyl, pyrrolyl, furanyl,thienyl or pyridyl and

R², R³, R⁴ and R⁵ are identical or different and each is independentlyof the others hydrogen or C₁ -C₁₂ -alkyl which may be substituted byhalogen, C₁ -C₁₂ -alkoxy, phenyl, substituted phenyl, C₁ -C₁₂-alkoxycarbonyl or by cyano,

with the proviso that when R⁵ is hydrogen the positions of thesubstituents CH₂ --L--O--CO--R¹ and R⁴ on either or both azulene ringsmay also be interchanged with each other within an azulene ring.

Preference is given to an optical recording medium which containsazulenesquaric acid dyes of the formula I where R², R³, R⁴ and R⁵ areeach C₁ -C₆ -alkyl or hydrogen.

Further preference is given to an optical recording medium containingazulenesquaric acid dyes of the formula I where R¹ is C₁ -C₁₂ -alkyl orC₁ -C₁₂ -alkenyl.

Particular preference is given to an optical recording medium whichcontains azulenesquaric acid dyes of the formula I where R² and R⁴ areeach methyl and R³ and R⁵ are each hydrogen.

Very particular preference is given to an optical recording medium whichcontains azulenesquaric acid dyes of the formula I where R² and R⁴ areeach hydrogen, R³ is ispopropyl and R⁵ is methyl.

Suitable base materials are conveniently transparent base materials suchas glass or plastics. Suitable plastics are for examplepoly(meth)acrylates, polycarbonates, polyesters, epoxies, polyolefins(e.g. polymethylpentene), polyamide, polyvinyl chloride, polystyrene andpolyvinyl esters.

A particularly preferred recording medium is based on a support ofpolycarbonate or poly(meth)acrylate, in particular polycarbonate.

Preference is further given to an optical recording medium whichcontains from 1 to 30% by weight, based on dye, of binder.

The novel azulenesquaric acid dyes of the formula I have good opticalcharacteristics. In addition, the novel compounds have been observed togive very stable pure dye layers. This is because no recrystallisationof the pure dye layer was observed and it is thus possible to dispensewith the addition of polymeric binders. Moreover, the lightfastness(stability) is significantly higher than that of existing methine dyes,so that the addition of stabilizers to the layer formulation can belimited to a minimum. Another particular advantage is the readysolubility of the novel dyes I in most organic solvents, so that thesedyes can be applied directly (without protective layer) to structuredplastics substrates, in particular polycarbonate substrates, byspincoating.

As mentioned above, the spincoating solution preferably contains abinder to ensure good long term stability and in particular to optimizeits viscosity. Preferably the solution contains from 1 to 30% by weight,based on the amount of dissolved solids in the solution, of a binder.

Suitable binders are for example polyorganosiloxanes, epoxides,poly(meth)acrylates, polystyrene homopolymers and copolymers,polyvinylcarbazole, polyvinylpyrrolidone, polyimidazole copolymers,polyvinyl ester copolymers, polyvinyl ether copolymers, polyvinylidenechloride polymers, acrylonitrile copolymers, polyvinyl chloride orcopolymers thereof, cellulose acetate and nitrocellulose.

A preferred recording medium contains a binder based on avinylpyrrolidone/vinyl acetate copolymer or a polyvinylchloride/polyvinyl ether copolymer.

The optical recording medium according to the present invention isadvantageously prepared by spincoating with a solution containing anorganic solvent and an azulenesquaric acid dye I, with or without abinder. Advantageously, the level of dissolved solids in the spincoatingsolution is from 1 to 30% by weight, based on the solution.

Suitable solvents are for example propanol, isopropanol, butanol,diacetone alcohol, methyl ethyl ketone, toluene, bromoform,1,1,2-trichloroethane and mixtures thereof.

Optionally, the solution may also contain up to 10% by weight, based onthe level of dissolved solids in the spincoating solution, of additives,for example antioxidants, singlet oxygen quenchers or UV absorbers.

Preferably, the spincoating solution contains up to 5% by weight, basedon the level of dissolved solids in the spincoating solution, of amixture of a plurality of antioxidants, singlet oxygen quenchers and UVabsorbers. When using antioxidants which likewise absorb in the nearinfrared, for example nickel thiolene complexes, as described forexample in DE-A-3,505,750, DE-A-3,505,751 or Dyes and Pigments 8 (1987),381-88, it is preferable for up to 10% by weight, based on the level ofdissolved solids in the spincoating solution, to be present in thesolution.

Spincoating is for the purposes of the present invention the applicationof the solution to a rotating base material, which advantageously has around shape. However, it is also possible to apply the solution to abase which is initially at rest and then set in rotation. The solutionis conveniently applied to the base by means of a syringe or capillaryor by means of a mechanical pump.

The base generally rotates at a speed of from 5 to 7000 rpm, preferablyfrom 500 to 5000 rpm, the solution being advantageously applied at arelatively low speed (about 500-2000 rpm) and then dried at a higherspeed (about 5000-7000 rpm). The thickness of the layer which issensitive to laser light is from 40 to 160 nm, preferably from 80 to 120nm. The thickness is dependent on the speed of rotation, theconcentration and viscosity of the spincoating solution and thetemperature.

In the optical recording medium according to the present invention, thelayer which is sensitive to laser light is present in the form of ahomogeneous, thin, smooth layer of high optical quality. For instance,the reflectivities are in general within a range greater than 12%.

The novel recording medium is also sufficiently sensitive to thewavelength of the laser light source used; that is, the incidence oflight pulses having an energy content of a few nJ which are focused to afocal spot diameter of ≦1 μm leads to the formation of pits with anexcellent signal-to-noise ratio.

Particularly suitable laser light sources on account of the small sizeof the device, its low energy consumption and the possibility of directmodulation of the optical output through modulation of the electricaldrive current are solid state injection lasers which emit in the nearinfrared, in particular the AlGaAs laser which emits within thewavelength range from about 750 to 900 nm.

The Examples which follow further illustrate the invention.

EXAMPLE 1

Preparation of 3-(7-isopropyl-1-methylazulen-4-yl)butyl acetate

4.8 g (0.063 mol) of acetyl chloride in 20 ml of dichloromethane wereadded dropwise at 0° C. to a solution of 12.1 g (0.05 mol) of3-(7-isopropyl-1-methylazulen-4-yl)butanol and 7.9 g (0.1 mol) ofpyridine in 100 ml of dichloromethane, and the mixture was stirred atroom temperature for 1 hour. It was then extracted with 30 ml of 2Nhydrochloric acid, and the organic phase was washed neutral and driedover sodium sulfate. The residue remaining behind after evaporating offthe solvent was chromatographed (silica gel; 9:1 v/v petroleumether/ethyl acetate). This gave 12.6 g (89%) of the acetate as a highlyviscous blue oil. Physical data: IR (KBr): 2959, 2929 (CH); 1741 (C═O);1555, 1463, 1436, 1387, 1365, 1241, 1047 cm⁻¹. ¹ H-NMR (CDCl₂): δ=1.38(d, 6H); 2.05 (s, 3H); 2.16 (cm, 2H); 2.68 (s, 3H); 3.08 (cm, 1H); 2.22(cm, 2H); 4.18 (cm, 2H); 6.95 (d, 1H); 7.30 (d, 1H); 7.40 (d, 1H); 7.64(d, 1H); 8.18 (s, 1H) ppm. ¹³ C-NMR (CDCl₃); δ=1286; 20.85; 24.72 (2C);30.17; 34.53; 38.28; 64.22; 112.19; 124.41; 125.46; 133.30; 135.13;136.39; 136.59; 137.28; 140.04; 147.55; 170.90 ppm. MS: m/e=284.4 (C₁₉H₂₄ O₂ ⁺, 50%).

The method of Example 1 was used to prepare the carboxylic esters listedin Table 1, which were characterized by IR, ¹ H-NMR, ¹³ C-NMR and MSspectra and also by GC.

If hydroxyalkylazulenes are reacted with crotonic or sorbic acidderivatives in the presence of stronger bases, e.g. triethylamine, then,in contradistinction to the above method, a partial or completeisomerization of the double bond takes place (see Example 2).

EXAMPLE 2

Preparation of 3-(7-isobutyl-1-methylazulen-4-yl)butyl3-butenecarboxylate

10.0 g (0.07 mol) of crotonyl chloride were added dropwise at roomtemperature to a solution of 7.26 g (0.03 mol) of3-(7-isobutyl-1-methylazulen-4-yl)butanol and 30 ml of triethylamine in100 ml of tetrahydrofuran, and the mixture was stirred for 2 hours. 50ml of water were then added, and the batch was thoroughly stirred. Itwas then extracted with methyl t-butyl ether, the extract was dried oversodium sulfate, the solvent was evaporated off, and the residueremaining behind was chromatographed over silica gel (9:1 v/v petroleumether/ethyl acetate). This gave 8.2 g (88%) of a product, which wasuniform according to GC, as a highly viscous blue oil. Physical data: IR(KBr): 2959, 2927 (CH); 1738 (C═O); 1464, 1423, 1388, 1327, 1256, 1173,921 cm⁻¹. ¹ H-NMR (CDCl₃): δ=1.47 (d, 6H); 2.18 (cm, 2H); 2.65 (s, 3H);3.08 (m, 3H), 3.20 (t, 2H); 4.18 (t, 2H); 5.18 (m, 2H); 5.94 (m, 1H);6.95 (d, 1H); 7.28 (bs, 1H); 7.40 (d, 1H); 7.62 (bs, 1H); 8.18 (s, 1H)ppm. ¹³ C-NMR (CDCl₃): δ=12.84; 24.71 (2C); 30.18; 34.50; 38.28; 39.23;64.41; 112.33; 118.36; 124.39; 125.47; 130.49; 133.28; 135.10; 136.42;136.60; 137.31; 140.04; 147.49; 171.29 ppm. MS: m/e=310.4 (C₂₁ H₂₈ O₂ ⁺,80%)

                                      TABLE 1                                     __________________________________________________________________________     ##STR10##                                                                    Example                                             IR (CO)                   No.  LOC(O)R.sup.1                 R.sup.2                                                                         R.sup.3                                                                            R.sup.4                                                                         R.sup.5                                                                          MS M.sup.D !                                                                        cm.sup.-1 !              __________________________________________________________________________    3    CH.sub.2CH.sub.2OC(O)CH.sub.  H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.19 H.sub.24 O.sub.2                                                     84.4 1741                            ##STR11##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.21 H.sub.28 O.sub.2                                                     284.4                                                                              1741                      5    CH.sub.2CH.sub.2OC(O)-t-Bu    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.22 H.sub.30 O.sub.2                                                     326.4                                                                              1728                      6    CH.sub.2CH.sub.2OC(O)(CH.sub.2).sub.3CH.sub.3                                                               H C(CH.sub.3).sub.2 H                                                                H CH.sub.3                                                                         C.sub.22 H.sub.30 O.sub.2                                                     26.5 1736                      7                                                                                   ##STR12##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.24 H.sub.34 O.sub.2                                                     354.5                                                                              1736                      8    CH.sub.2CH.sub.2OC(O)(CH.sub.2).sub.8CH.sub.3                                                               H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.27 H.sub.40 O.sub.2                                                     96.6 1734                      9    CH.sub.2CH.sub.2OC(O)CHCH.sub.2                                                                             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.20 H.sub.24 O.sub.2                                                     96.4 1724                      10                                                                                  ##STR13##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.22 H.sub.28 O.sub.2                                                     24.5 1726                      11                                                                                  ##STR14##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.21 H.sub.26 O.sub.2                                                     10.4 1718                      12                                                                                  ##STR15##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.23 H.sub.30 O.sub.2                                                     38.5 1719                      13   CH.sub.2CH.sub.2OC(O)CHCHCH.sub.3                                                                           H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.21 H.sub.26 O.sub.2                                                     10.4 1720                      14                                                                                  ##STR16##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.23 H.sub.30 O.sub.2                                                     38.5 1721                      15   CH.sub.2CH.sub.2OC(O)CHCHCHCHCH.sub.3                                                                       H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.23 H.sub.28 O.sub.2                                                     36.5 1713                      16                                                                                  ##STR17##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.25 H.sub.32 O.sub.2                                                     64.5 1713                      17                                                                                  ##STR18##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.26 H.sub.25 O.sub.2                                                     72.5 1712                      18                                                                                  ##STR19##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.28 H.sub.32 O.sub.2                                                     00.6 1712                      19                                                                                  ##STR20##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.22 H.sub.24 O.sub.3                                                     36.4 1728                      20                                                                                  ##STR21##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.24 H.sub.28 O.sub.3                                                     64.5 1727                      21                                                                                  ##STR22##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.24 H.sub.26 O.sub.2                                                     46.5 1718                      22                                                                                  ##STR23##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.26 H.sub.30 O.sub.2                                                     74.5 1718                      23                                                                                  ##STR24##                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         C.sub.26 H.sub.30 O.sub.2                                                     74.5 1715                      __________________________________________________________________________

EXAMPLE 25

Preparation of the bis 3-(7-isobutyl-1-methylazulen-4-yl)butylacetate!squaric acid dye

A mixture of 15.9 g (0.056 mol) of3-(7-isobutyl-1-methylazulen-4-yl)butyl acetate, 5.0 g of squaric acidand 80 ml of 1:1 toluene/butanol was refluxed for 2 hours under a waterseparator. After the solvent had been distilled off, the residue wasrecrystallized from ethyl acetate. This gave 3.0 g (17%) of the dye asmetallically shiny, pale brown crystals of melting point 180°-181° C.Physical data: IR (KBr): 2985 (CH); 1736, 1612 (C═O); 1437, 1386, 1337,1323, 1252, 1243, 1020 cm⁻¹, UV (CH₂ Cl₂): λmax(ε)=766 (116000) nm. ¹H-NMR (CDCl₃): δ=1.38 (d, 12H); 1.89 (s, 6H); 1.95 (m, 4H); 2.55 (s,6H); 3.08 (cm, 2H); 3.95 (m, 8H); 7.48 (d, 2H); 7.60 (d, 2H); 8.12 (s,2H); 8.88 (s, 2H) ppm. ¹³ C-NMR (CDCl₃): δ=12.96 (2C); 20.73 (4C); 24.21(2C); 30.53 (2C); 36.17 (2C); 38.33 (2C); 63.66 (2C); 121.58 (2C);130.87 (2C); 133.97 (2C); 134.38 (2C); 138.18 (2C); 139.82 (2C); 141.84(2C); 147.49 (2C); 150.31 (2C); 155.54 (2C); 170.75 (2C); 181.79 (2C);183.07 (2C) ppm. MS: m/e 646.8 (C₄₂ H₄₄ O₈, 50%).

The method of Example 24 was used to prepare the squaric acid dyeslisted in Table 2, which were additionally characterized by IR, ¹ H-NMR,¹³ C-NMR and MS spectra.

                                      TABLE 2                                     __________________________________________________________________________     ##STR25##                                                                    Example                                 .sup.λ max                                                                  m.p..(g)                         No.  LOC(O)R.sup.1          R.sup.2                                                                         R.sup.3                                                                            R.sup.4                                                                         R.sup.5                                                                          CH.sub.2 Cl.sub.2                                                                   °C.!                     __________________________________________________________________________    25                                                                                  ##STR26##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         768 (108000)                                                                       167-167                          26   CH.sub.2CH.sub.2OC(O)-t(Bu)                                                                          H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         768 (102000)                                                                       189                              27   CH.sub.2CH.sub.2OC(O)(CH.sub.2).sub.3CH.sub.3                                                        H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         768 (113000)                                                                       181-182                          28                                                                                  ##STR27##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         768 (1113000)                                                                      163-164                          29   CH.sub.2CH.sub.2OC(O)(CH.sub.2).sub.8CH.sub.3                                                        H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         765 (111000)                                                                       70-72                            30   CH.sub.2CH.sub.2OC(O)CHCH.sub.2                                                                      H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         769 (112000)                                                                       115-116                          31                                                                                  ##STR28##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         772 (107000)                                                                       99-101                           32                                                                                  ##STR29##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         770 (117000)                                                                       135-136                          33                                                                                  ##STR30##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         773 (111000)                                                                       171-172                          34   CH.sub.2CH.sub.2OC(O)CHCHCH.sub.3                                                                    H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         770 (114000)                                                                       183-184                          35                                                                                  ##STR31##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         772 (106000)                                                                       103-105                          36   CH.sub.2CH.sub.2OC(O)CH.sub.2CHCH.sub.2                                                              H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         770 (118000)                                                                       97-98                            37   CH.sub.2CH.sub.2OC(O)CHCHCHCHCH.sub.3                                                                H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         770 (115000)                                                                       129-130                          38                                                                                  ##STR32##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         772 (114000)                                                                       213-214                          39                                                                                  ##STR33##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         768 (117000)                                                                       172-173                          40                                                                                  ##STR34##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         772 (118000)                                                                       180-181                          41                                                                                  ##STR35##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         766 (118000)                                                                       200-201                          42                                                                                  ##STR36##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         770 (108000)                                                                       163-164                          43                                                                                  ##STR37##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         768 (123000)                                                                       230-231                          44                                                                                  ##STR38##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         771 (120000)                                                                       207                              45                                                                                  ##STR39##             H C(CH.sub.3).sub.2  H                                                               H CH.sub.3                                                                         767 (117000)                                                                       183-185                          __________________________________________________________________________

EXAMPLE 46

An approximately 5% strength by weight solution of the dye of Example 24in 1:1 v/v propanol/diacetone alcohol was applied with a syringe to apolymethyl methacrylate disk rotating at about 2000 rpm, and theremaining solvent was then spun off at 5000 rpm. This produced ahomogenous, highly reflective dye layer which was very readily writablewith a semiconductor laser (λ=830 nm). The data can be read back withvery good contrast.

EXAMPLE 47

A 3% strength by weight solution of the dye of Example 24 in 1:1 v/vpropanol/diacetone alcohol which contained 30% by weight, based on thelevel of dissolved solids in the solution, of polymethyl methacrylatewas applied to a grooved polycarbonate disk by spincoating as describedin Example 46. This produced a homogeneous, highly reflective dye layerwhich is firmly adherent to the substrate, gives a good image of thegrooves on the substrate and is very readily writable with asemiconductor laser (λ=830 nm). The written data were stable under hotmoist conditions and can be read back with good contrast as often asdesired.

EXAMPLE 48

A 2% strength by weight solution of the dye of Example 24 in 1:1 v/vpropanol/diacetone alcohol which, based on the level of dissolved solidsin the solution, contained 10% by weight of phenolic resin as binder and5% by weight of 4-octyl-4'-fluorodiphenyldithiolenenickel as stabilizerwas applied to a grooved polycarbonate disk by spincoating as describedin Example 46. The storage layer obtained is similar in all respects tothat of Example 47, but is more stable to UV light.

EXAMPLE 49

A 2% strength by weight solution of the dye of Example 24 in toluenewhich, based on the level of dissolved solids in the solution, contained10% by weight of polymethyl methacrylate and 5% by weight ofbiscampheratodithiolenenickel was applied to a glass disk by spincoatingas described in Example 46. The resulting dye layer was homogeneous andshowed a high background reflectivity. It was readily writable with asemiconductor laser (λ=780 nm). The written data are stable under theusual test conditions and can be read back as often as desired.

We claim:
 1. A carbonyloxy-substituted azulenesquaric acid dye of theformula I ##STR40## where L is C₁ -C₁₂ -alkylene which may besubstituted by phenyl,R is monounsaturated or polyunsaturated C₁ -C₁₂-alkenyl, which may be phenyl-substituted, C₅ -C₇ -cycloalkenyl,pyrrolyl, furanyl, thienyl or pyridyl and R², R³, R⁴ and R⁵ areidentical or different and each is independently of the others hydrogenor C₁ -C₁₂ -alkyl, which may be substituted by halogen, C₁ -C₁₂ -alkoxy,phenyl, substituted phenyl, C₁ -C₁₂ -alkoxycarbonyl or by cyano,with theproviso that when R⁵ is hydrogen the positions of the substituents CH₂--L--O--CO--R¹ and R⁴ on either or both azulene rings may also beinterchanged with each other within an azulene ring.
 2. Anazulenesquaric acid dye as claimed in claim 1, wherein R², R³, R⁴ and R⁵are each C₁ -C₈ -alkyl or hydrogen.
 3. An azulenesquaric acid dye asclaimed in claim 1, wherein R² and R⁴ are each methyl and R³ and R⁵ areeach hydrogen.
 4. An azulenesquaric acid dye as claimed in claim 1,wherein R² and R⁴ are each hydrogen, R³ is isopropyl and R⁵ is methyl.